A widely used medium for storing data is magnetic tape. Tape cartridges are one of the most popular formats for storing data on tape. Two widely used tape cartridges are the dual reel cartridge and the single supply reel cartridge. In a dual reel tape cartridge, both the supply reel and the take-up reel are housed in the cartridge. In a single supply reel tape cartridge, the take-up reel is built into the tape drive along with an automatic tape threading mechanism. Tape drives often use several sensors to sense the position of the cartridge as it is loaded into the drive. The information from the sensors allows the tape drive controller to monitor cartridge loading.